Epoxy resin composition containing reactive flame retardant phosphonate oligomer and filler

ABSTRACT

An epoxy resin composition is disclosed that comprises an epoxy resin, a reactive phosphonate curing agent, an inorganic filler, whose presence allows for reduced amounts of phosphonate as compared to a composition not containing the filler, an optional polybenzoxazine resin, and an optional co-curing agent.

The present invention relates to an epoxy resin composition that can beused, for example, in printed wiring boards for electronic applicationsand that represents a novel improvement, for example, over the type ofcompositions described in Japanese Patent Publication No. 2001/302,879to Shin Kobe Electric Manufacturing Co. Ltd./Hitachi Chemical Co. Ltd.

The composition of the present invention contains, as one essentialcomponent, an epoxy resin. This component is present at from about 20%to about 50%, by weight of the total weight of the composition.Preferably, this component is a non-halogen containing epoxy resin, suchas a bisphenol A-type of epoxy resin, or other resins of this generaltype that have utility for the manufacture of printed wiring boards orother electronic substrate materials of that type (bisphenol F epoxy,phenolic novolak epoxy, cresol novolak epoxy, and/or bisphenol A novolakepoxy resins). Compatible mixtures of any of these resins may beemployed.

An additional optional, but preferred, component for the compositions ofthe present invention is a polybenzoxazine resin in an amount of up toabout 50%, by weight of the total weight of the composition, preferably,from about 5% to about 20%, by weight. This composition is athermosetting resin that contains a dihydrobenzoxazine ring that isformed by the reaction depicted below:

This component and its process of manufacture is further described inU.S. Pat. No. 5,945,222 (at Col. 2, line 59 to Col. 3, line 62), whichis incorporated herein by reference.

The next additional optional component of the composition of the presentinvention is a co-curing agent for the aforementioned resincomponent(s). Mixtures of compatible co-curing agents can be used. Thisco-curing agent will be present at from about 0% to about 20%, by weightof the total weight of the composition, preferably from about 5% toabout 15%, by weight. Representative co-curing agents include, phenol-formaldehyde, cresol- formaldehyde, novolac, novolac/melamine,phosphorylated novolac, triazine-modified novolac resins, dicyandiamide,and the like.

The compositions of the present invention also contain one or moreinorganic filler material(s) at from about 10% to about 50%, by weight.The filler material or materials can be selected from such known fillersas: talc, silica, alumina, aluminum hydroxide, magnesium hydroxide, zincborate, and the like. A preferred material for use herein is aluminatrihydrate.

While PCT Published Patent Application No. WO 03/029258 teaches thatepoxy resins can contain a hydroxy-terminated oligomeric phosphonate asa flame retardant, that PCT application generally shows that the levelof such phosphonate needs to be in the neighborhood of from about 20% toabout 30%, by weight of the epoxy resin, or higher for acceptableresults. No use of filler in such compositions is mentioned. Inaccordance with the present invention, the additional presence of fillerhas allowed for the use of lower amounts of the phosphonate additive. InTable I, which is given below, Example 7 illustrates that only 10% ofthe phosphonate was needed. The use of the filler allows for theproduction of a sufficiently flame retarded epoxy composition, despitethe use of lower amounts of phosphonate flame retardant, while stillproducing a product having good physical properties (such as, higherT_(g), better hydrolytic stability, etc).

Each of the foregoing components of the present composition areindividually known to persons of ordinary skill in the art as potentialcomponents for epoxy compositions of the present type, and they havebeen employed in various combinations heretofore, as exemplified by theaforementioned Japanese Patent Publication No. 2001/302,879.

The reactive phosphonate curing agent that forms a novel and essentialadditive herein, as compared to prior art approaches that relied uponvarying combinations of the previously described components, is presentat from about 3% to about 40%, by weight of the total weight of thecomposition, preferably from about 5% to about 20%, by weight. Thisflame retardant curing agent, as more fully described in PCTInternational Patent Publication No. WO 03/029258, is an oligomericphosphonate comprising the repeating unit —OP(O)(R)—O-Arylene- and has aphosphorus content of greater than about 12%, by weight. The phosphonatespecies in the composition comprise those containing —OH end groups aswell, possibly, of those not containing —OH end groups. The preferred Rgroup is methyl, but can be any lower alkyl group.

By “Arylene” is meant any radical of a dihydric phenol. The dihydricphenol preferably should have its two hydroxy groups in non-adjacentpositions. Examples include the resorcinols; hydroquinones; andbisphenols, such as bisphenol A, bisphenol F, and 4,4′-biphenol,phenolphthalein, 4,4′-thiodiphenol, or 4,4′-sulfonyldiphenol. TheArylene group can be 1,3-phenylene, 1,4-phenylene, or a bisphenoldiradical unit, but it is preferably 1,3-phenylene.

This component for the epoxy resin composition of this invention can bemade as described in PCT Patent Application 03/029258 by any of severalroutes: (1) the reaction of an RPOCl₂ with HO-Aryl-OH or a salt thereof,where R is lower alkyl, preferably methyl; (2) the reaction of diphenylalkylphosphonate, preferably methylphosphonate, with HO-Arylene-OH undertransesterification conditions; (3) the reaction of an oligomericphosphite with repeating units of the structure —OP(OR′)—O-Arylene- withan Arbuzov rearrangement catalyst, where R′ is lower alkyl, preferablymethyl; or (4) the reaction of an oligomeric phosphite with therepeating units having the structure —OP(O-Ph)—O-Arylene with trimethylphosphite and an Arbuzov catalyst or with dimethyl methylphosphonatewith, optionally, an Arbuzov catalyst-. The —OH end groups, if attachedto Arylene can be produced by having a controlled molar excess of theHO-Arylene-OH in the reaction media. The —OH end groups, if acid type(P—OH), can be formed by hydrolytic reactions. It is preferred that theend groups of the oligomers be mainly -Arylene-OH types.

The epoxy resin composition of the present invention can containoptional additives as well including the following types of materials:fiber and/or cloth reinforcing additives; release agents; colorants; andthe like.

EXAMPLES

Materials

Epoxy—bisphenol A type epoxy resin

Novolac—phenol-formaldehyde resin (novolac type) (auxiliary curingagent)

Melamine-novolac—copolymer of phenol, melamine and formaldehyde(auxiliary curing agent)

Phosphor-novolac—phosphorylated phenol-formaldehyde resin (auxiliarycuring agent)

ATH—aluminum trihydrate

Phosphonate—reactive phosphonate curing agent where “arylene” isresorcinol

DICY—dicyandiamide (auxiliary curing agent)

AMI-2—-2-methylimidazole (catalyst)

BDP—bisphenol A bis(diphenyl phosphate) Akzo Nobel brand FYROLFLEX BDP

BDP(OH)—Bisphenol A diphenylphosphate

made as described in U.S. Pat. No. 3,090,799.

RDP(OH)₂ resorcinol bis(phenylresolcinyl phosphate)

made as described in U.S. Pat. No. 5,508,462.

Experimental

T_(g)—glass transition temperature measured in TMA experiments asdescribed in IPC-TM-650 protocol.

UL 94—flammability rating according to UL 94 vertical protocol (V-0,V-1, V-2)

PCT—time of exposure to steam in Pressure Cooker Test according toIPC-TM-650 protocol. Water absorption was measured after removal of thespecimen from the autoclave.

Delamination—measured in TMA experiments at 260 or 288° C. as describedin IPC-TM-650 protocol

CTE—coefficient of thermal expansion measured in TMA experiments at thetemperatures below and above glass transition (<T_(g) and >T_(g)respectively). IPC-TM-650 protocol was followed.

Tables I and II that are reproduced below sets forth a number offormulations that represent embodiments of the present invention. TableIII shows set of comparative formulations. TABLE I Example 1 2 3 4 5 6 78 Component Epoxy, wt. % 45 45 40 40 40 40 40 40 Novolac, wt. % 10 10 55 ATH, wt. % 25 25 35 35 35 30 50 50 Phosphonate, wt. % 20 20 20 20 2530 10 9 DICY 1 AMI-2, wt. % 0.25 0.5 0.25 0.25 0.1 0.25 0.25 Physicalproperty T_(g), ° C. 130 130 110 120 140 110 120 130 UL-94, rating FailFail V-1 V-0 Fail Fail V-0 V-0 PCT, time (min)/pass (fail) 60/F 60/F30/F 60/F 60/F 60/P 30/P 30/F water absorption, % 0.4 0.4 0.3 0.3 0.10.2 0.3 Delamination at 260° C., min >60 288° C.,min >60 >60 >60 >60 >60 CTE, <T_(g), 10⁶ mm 50 40 40 30 40 >T_(g), 10⁶mm 250 250 200 160 195

TABLE II Example 9 10 11 12 13 14 15 16 Component Epoxy, wt. % 30 20 2020 40 35 20 20 Novolac, wt. % 10 10 5 5 Melamine-novolac, wt. % 15 10 105 PBZ, wt. % 15 15 15 15 15 15 ATH, wt. % 25 35 50 50 25 35 35 50Phosphonate, wt. % 20 20 10 10 20 20 20 10 AMI-2, wt. % 0.25 0.25 0.250.25 0.25 0.25 0.25 Physical property T_(g), ° C. 140 150 190 130 120160 UL-94, rating Fail V-1 V-0 V-0 Fail V-1 V-1 V-0 PCT, time (min)/pass(fail) 60/P 90/P 90/P 90/F 120/P 120/P 90/P 90/F water absorption, % 0.81.2 0.3 0.5 1.0 0.9 1.2 0.2 Delamination at 260° C., min 5 5 288° C.,min >60 >60 >60 CTE, <T_(g), 10⁶ mm 30 30 30 40 35 40 >T_(g), 10⁶ mm 160130 160 160 200 165

TABLE III (comparative) Example 17 18 19 20 21 Component Epoxy, wt. % 4035 35 35 35 Phosphor-novolac, wt. % 15 10 Melamine-novolac, wt. % 10 1010 BDP, wt. % 20 BDP(OH), wt. % 20 RDP(OH)₂, wt. % 20 Phosphonate, wt. %20 20 ATH, wt. % 25 35 35 35 35 AMI-2, wt. % 0.25 0.25 0.25 0.25 0.25Physical property T_(g), ° C. 100 115 120 120 UL-94, rating Fail V-1Fail Fail Fail PCT, time (min)/pass 60/F 60/F 30/F 60/F 120/P (fail)water absorption, % 0.4 0.4 0.2 0.3 0.6 Delamination at 260° >60 C., min288° C., min 20 >60 >60 >60 CTE, <T_(g), 10⁶ mm 50 50 65 60 >T_(g), 10⁶mm 230 240 210 200

1. An epoxy resin composition comprising an epoxy resin; a reactivephosphonate curing agent; an inorganic filler; an optionalpolybenzoxazine resin; and an optional co-curing agent.
 2. A compositionas claimed in claim 1 wherein the epoxy resin comprises from about 10%to about 50%, by weight of the total weight of the composition.
 3. Acomposition as claimed in claim 1 wherein reactive phosphonate curingagent comprises from about 5% to about 30% by weight, of the totalweight of the composition.
 4. A composition as claimed in claim 1wherein the polybenzoxazine resin comprises up to about 50%, by weightof the total weight of the composition.
 5. A composition as claimed inclaim 1 wherein the co-curing agent comprises from about 5% to about20%, by weight of the total weight of the composition.
 6. A compositionas claimed in claim 1 wherein the inorganic filler comprises from about10% to about 50%, by weight, of the total weight of the composition. 7.A composition as claimed in claim 1 wherein the epoxy resin comprisesfrom about 10% to about 50%, by weight of the total weight of thecomposition, the reactive phosphonate curing agent comprises from about5% to about 30%, by weight, of the total weight of the composition, theinorganic filler comprises from about 10% to about 50%, by weight of thetotal weight of the composition, and the benzoxazine resin comprisesupto about 50%, by weight of the total weight of the composition.
 8. Acomposition as claimed in claim 7 further comprising a co-curing agentat from about 5% to about 20%, by weight of the total weight of thecomposition.
 9. A composition as claimed in claim 1 wherein theco-curing agent is selected from the group consisting of novolac,melamine-novolac, and phosphor-novolac compositions.
 10. A compositionas claimed in claim 2 wherein the co-curing agent is selected from thegroup consisting of novolac, melamine-novolac, and phosphor-novolaccompositions.
 11. A composition as claimed in claim 3 wherein theco-curing agent is selected from the group consisting of novolac,melamine-novolac, and phosphor-novolac compositions.
 12. A compositionas claimed in claim 4 wherein the co-curing agent is selected from thegroup consisting of novolac, melamine-novolac, and phosphor-novolaccompositions.
 14. A composition as claimed in claim 6 wherein theco-curing agent is selected from the group consisting of novolac,melamine-novolac, and phosphor-novolac compositions.
 15. A compositionas claimed in claim 8 wherein the co-curing agent is selected from thegroup consisting of novolac, melamine-novolac, and phosphor-novolaccompositions.